Array.prototype.random = function(limit)
              {
        	if (typeof limit == 'undefined' || limit < 0) limit = 1;
        	else if (!limit) limit = this.length;
        	for (var i = 0, source = this, target = new Array(), n = source.length; i < limit && n > 0; i++)
        	{
        		do { var index = Math.random(); } while (index == 1);
        		index = Math.floor(index * n);
        		target.push(source[index]);
        		source[index] = source[--n];
        	}
        	return target;
                }